The different styles of bearings
Loose ball, loose ball in a retainer, needle, and cartridge are the main styles of bearing founds in cycling frames and components.
Loose ball bearings
Loose ball bearings are the most traditional and require the use of bearings with a mated cup and cone. Although they’re the oldest, in many ways they can be superior. They are angular contact (more on this later) and offer excellent maintenance and performance characteristics.
The same can be said for loose ball in a retainer, but generally speaking this became popular in more cost-effective versions. In short, its attractiveness comes from the fact it’s quick and easy. Unfortunately, what makes it quick and painless — the retainer — also contributes to its average performance.
Needle bearings
Needle bearings (aka roller bearings) are becoming uncommon, except for in pedals, and even then they’ve lost a lot of ground to newer and cheaper tech.
They’re just like they sound — instead of ball bearings, they’re in the shape of a needle or cylinder.
They can create incredibly smooth rolling and stable platforms, especially under high loads, but in the cycling industry there’s a tendency to shy away from them due to the expense of creating good mating surfaces.
When not mated properly, they tend to fatigue quickly. Needle bearings often get replaced by multiple rows of cartridge bearings.
Cartridge bearings
Cartridge bearings have come to the forefront in recent years as a result of ever-increasing tolerances in hub, frame, and component bores.
Cartridge systems require precision to function well, and as technology trickles down, so does the frequency of their application.
The balls, cup and cone are contained in a cartridge that can be installed into a waiting bore. While having everything neatly packaged seems simple, the reality couldn’t be different, but the benefits seem to outweigh the skillset and tools required to maintain them.
The bearing diameters
Loose ball-bearing systems require a measurement of ball diameter, which is something like 3/16in (4.7625 mm).
There are other corresponding measurements required to overhaul balls and cone systems and your bike shop will be able to tell you more. More often than not, just replacing the balls is a great start (but bear in mind cup and cone dimensions can be challenging to find, depending on the brand and the age of the system).
As for cartridge, inside diameter (ID), outside diameter (OD) and width all contribute to bearing size, which directly correlates to bearing life. The measurements take the form of ‘15x24x5mm’ or similar. They often have a corresponding universal identifier, which in the case of the aforementioned bearing, would be 6802, for instance.